In certain types of passive automotive vehicle occupant restraint systems, the electric firing circuit for causing deployment of a passive occupant restraint device (such as an air bag) comprises an arming switch portion and a discriminating switch portion, the latter portion containing plural discriminating switches. Both arming and discriminating switches are inertia switches which are actuated in response to certain velocity changes. A principal purpose in employing both an arming switch portion and a discriminating switch portion in the firing circuit is to distinguish the concurrence of conditions that do not call for deployment of the restraint device from the concurrence of conditions that do. For example, a mechanic who, during the process of repairing or adjusting an automobile, hammers at the front of the vehicle with sufficient force might cause a discriminating switch in the vicinity to be sufficiently impacted that it activates. In the absence of an arming switch in the circuit, the restraint device would be unintentionally deployed. An arming sensor, therefore, is intended to prevent such an unintentional deployment.
The assignee of this patent application currently produces a switch assembly consisting of two switch elements mounted in a single metal housing. This product is sometimes called a "dual sensor", and it provides both an arming switch function and a discriminating switch function. The product is fairly large and more expensive to produce than single sensors used individually as individual arming switches and as individual discriminating switches.
The present invention relates to a new and unique construction for a combination arming/discriminating switch assembly in which a single inertia sensing mass is associated with both an arming switch portion and a discriminating switch portion. The present invention offers a number of significant advantages such as: reduction in the number of component parts; reduction in the number of moving parts; reliability improvement; smaller packaging size; and reduction in labor and material costs.
The incorporation of multiple switches into an inertia switch assembly is not per se novel as evidenced by U.S. Pat. Nos. 3,889,130 and 4,097,699, which Were developed in connection with a limited search conducted on the present invention. It is believed that the particular configuration of arming and discriminating switches in an inertia switch assembly as hereinafter described and claimed, has not heretofore been contemplated. The ensuing Description Of The Preferred Embodiment discloses principles of the invention with reference to the accompanying drawings illustrating an exemplary embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.